The present disclosure relates to a measurement device and a measurement method.
Sound localization techniques include an out-of-head localization technique, which localizes sound images outside the head of a listener by using headphones. The out-of-head localization technique localizes sound images outside the head by canceling characteristics from the headphones to the ears and giving four characteristics from stereo speakers to the ears. Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2002-209300) discloses a method using a head-related transfer function (HRTF) and an ear canal transfer function as a method for localizing sound images outside the head. Further, it is known that the HRTF varies widely from person to person, and particularly, the variation of the HRTF due to a difference in auricle shape is significant.
In out-of-head localization reproduction, transfer characteristics measurement signals (impulse sounds etc.) that are output from 2-channel (which is referred to hereinafter as “ch”) speakers are recorded by microphones placed on the listener's ears. Then, a head-related transfer function is calculated based on impulse responses, and a filter is generated. The generated filter is convolved to 2-ch music signals, thereby implementing out-of-head localization reproduction.
The characteristics can be measured accurately by placing microphones on the ears (preferably, at the entrances of the ear canals) of a listener. However, it is complicated to carry out measurement with microphones at the entrances of the ear canals of a listener. Patent Literature 2 discloses a method of measuring the transfer characteristics by headphones equipped with microphones.